1. Field of the Invention
The present invention generally relates to a system in a vehicle and method for range and lateral position measurement of a preceding vehicle on the road.
2. Description of Related Art
Radar and stereo camera systems for adaptive cruise control (ACC), have been already introduced into the market. Recently, radar has been applied to pre-crash safety system, collision avoidance and low speed follower (LSF) systems. Typically, the range and lateral position measurement of a preceding vehicle is accomplished utilizing radar and/or stereo camera systems. Radar systems can provide a very accurate range. However, millimeter wave type radar systems such as 77 GHz systems are typically quite expensive. Laser radar is low cost, but requires mechanical scanning. Further, radar, while good for range determination is generally, not well suited to identify the object and give an accurate lateral position.
Stereo camera systems can determine the range and identify the lateral position of an object. However, these systems are typically difficult to maintain the accuracy due to the accurate alignment required between the two cameras. They are also expensive requiring two image processors, twice as many image processors as a single camera system.
Further, both conventional camera and radar systems can be easily confused by multiple objects in an image. For example, multiple vehicles in adjacent lanes and roadside objects can be easily interpreted as a preceding vehicle in the same lane as the vehicle carrying the system. In addition, brightness variation in the background of the image, like the shadows of vehicles and roadside objects, can also increase the difficulty for these systems to identify the vehicle.
In view of the above, it can be seen that conventional ACC or LSF systems may have difficulty identifying vehicles due to a complex background environment. Further, it is apparent that there exists a need for an improved system and method for identifying and measuring the range and lateral position of the preceding vehicle with low cost.